fredrussell
Well-Known Member
Double post.
High capacity DC breakers
- Thread starter Sea Change
- Start date
fredrussell
Well-Known Member
No, have a good read of it. Op seems to be very knowledgeable in this area, and has the equipment to provide actual figures. It’s a long and tedious thread I’ll admit, but what I take from it is that the American boating authority has picked a class T fuse as the best fuse because it’s good enough for pretty much any size battery bank one is likely to have on a boat. But if your battery bank is a ‘smaller’ one, you can use certain other fuses such as MRBF safely.
Sea Change
Well-Known Member
I'm surprised he rates ANL so highly. I haven't come across any figures that suggest they are as high AIC as MRBF.
Sea Change
Well-Known Member
Thanks, that's about the price I was expecting and indeed similar to what I was paying four or five years ago.
Shipping to the US sends pretty risky at the moment, however I'm thinking of sending over some NH fuses as they're about £5 a go so I'd they get impounded it's no great loss. They're very hard to get hold of over there.
Seeing as I'm moving to a four battery setup, spending £100 on a fuse and holder for each battery really adds up...
PaulRainbow
Well-Known Member
Sorry but i don't have the time or inclination to read long forum posts by random blokes. If you want to follow his advice rather than go by that of established best practice that's up to you.
Personally, although i'm not obliged to do so, i follow the ABYC guidelines as much as possible. If i'm asked by an insurance company for details/specs of an install i can provide acceptable details to them.
This is a perfect example of why insurance companies don't want DIY installs.
fredrussell
Well-Known Member
Well, fair enough then. Will Prowse is some random bloke of the internet but we all seem to accept that he’s put in the hard work and not just plucking facts and figures from thin air. This being a relatively new field I think it’s a question of trying to work out which sources of info can be trusted. The one I linked to seems to me to have also done the hard work and provided proof of that. I totally accept and understand that as a professional you have to go by the official recommendation, which, in the absence of any UK ‘legislation’, is that of the ABYC.
Sea Change
Well-Known Member
I'm not a big fan of 'just get a professional to do it'. As far as I'm aware, anybody can call themselves a marine electrician. I've seen a 'pro' lithium installation protected only by an ANL fuse. Another where tens of thousands of dollars had been spent and Victron components were melting (don't try to run 1000A at 12v 
).
I suspect I'm similar to most Practical Boat Owners in that I like to fully understand all of the systems on my boat, and do most of the work myself.
There are good professionals, and there are cowboys. We're lucky to have people like Paul on here who knows what he's doing and is willing to share his knowledge. Picking his brains is part of what I consider due diligence. But just because I'm asking about a certain way of doing something doesn't mean I'm endorsing it.
By the way, I asked about these breakers on a Facebook group, and somebody posted a video where a German guy was putting them through their paces. The 160A breaker ran for over an hour at 250A, and even at 350A took over three minutes to blow.
So, that's a no from me.
).I suspect I'm similar to most Practical Boat Owners in that I like to fully understand all of the systems on my boat, and do most of the work myself.
There are good professionals, and there are cowboys. We're lucky to have people like Paul on here who knows what he's doing and is willing to share his knowledge. Picking his brains is part of what I consider due diligence. But just because I'm asking about a certain way of doing something doesn't mean I'm endorsing it.
By the way, I asked about these breakers on a Facebook group, and somebody posted a video where a German guy was putting them through their paces. The 160A breaker ran for over an hour at 250A, and even at 350A took over three minutes to blow.
So, that's a no from me.
Trident
Well-Known Member
The guy you linked to is an experienced engineer and his tools for the test and methodology are good. I have seem similar tests by several experts and all agree (as I noted in an earlier post) that many factors can reduce the IRC meaning that sometimes non Class T fuses can be used successfully BUT, not every case will have the resistance he found, almost no one will actually check before making a decision and even if they do they may or may not know what they are actually looking at. And I doubt that an insurer would even look at the information that anyone, even a professional, might supply, if it goes against "perceived best practice" / "reasons we can get out of paying"
It's interesting information and I have my own experience where a standard Mega fuse worked perfectly to protect a 600ah LFP bank - nice loud bang and a flash and everything cut off (I came to fix a DIY job , I did not fit it, ) where the customer had a big battery pack supplying a 2kw inverter and then wired up a 3.5kw domestic oven to it, hence the bang - as the inverter had a cut off after 3 seconds at over rated capacity that means the fuse blew before 3 seconds (200 amp mega fuse) . But, we KNOW class T will work every time and is what insurers look for, we only know that in some cases "lesser" fuses will work due to the resistance in the chain. Why risk it?
Trident
Well-Known Member
Can you make it a two battery set up with 2 fuses? If you have the JK BMS that will run 8 cells (as do many others) so you can have two 600ah packs instead of 4, 300 ah packs. Also saves the cost of two expensive BMS ? Just a thought..
Sea Change
Well-Known Member
Good idea but the batteries are already made up.
Tbh if I'd known from the start that I'd end up with this many batteries, I would have gone 24v from the outset. But it's a bit late for that, I'm not buying a new inverter now...
Having ruled out the breakers, I'm leaning towards NH. They're no more expensive than MRBF, with the highest AIC out of all the options. I'll still need to buy separate isolators for each battery
(Question- why is this considered necessary in a lithium bank when we never do it with lead acid?)